The days of cast-iron pipe, with rigid dimensions, have passed in fluid distribution systems for utilities, such as heating gas distributors. Today, plastic pipes are universally used. They are cheaper, car be joined by simple heating techniques, and deteriorate at a much slower pace than metal pipes. However, plastic pipes are much less rigid than cast-iron pipes and when wound, as they are, into large coils for transportation and storage, they tend to become oval, rather than circular, in cross-section. If the ovality of a pipe becomes excessive, it cannot be joined with another pipe in the course of installing a distribution network. Since thousands of feet of pipe may be involved in an installation, unusable pipe results in an unnecessary and unacceptable expense. Thus, the burden is shifted to the incoming inspection and quality control departments of producers and large-scale users of plastic pipe. Ovality and wall thickness must be checked before the pipe is sent out into the field and at the time a joinder to another pipe is attempted in the field. Therefore, it is an object of this invention to provide a gauge which may be used quickly and with a minimum of training, to determine whether or not a plastic pipe exceeds a predetermined limit on ovality. A related object of the invention is to provide a set of gauges which may be used to determine the degree of ovality of a plastic pipe or to determine whether or not plastic pipes of different diameters exceed a predetermined ovality limit.